Golf ball with cover made from fast curing polyurethane

ABSTRACT

A golf ball includes a wound center and a cover made from fast curing polyurethane. The fast curing polyurethane is a two-component polyurethane which includes an isocyanate and a mixture of isocyanate reactive compounds comprising polyether or polyester polyol, aliphatic or aromatic (di) amines, and chain extenders, catalysts, internal mold release agent as needed.

RELATED APPLICATION

[0001] This application is a continuation-in-part of co-pendingapplication Ser. No. 09/624,703, filed Jul. 24, 2000.

BACKGROUND

[0002] This invention relates to golf balls, and, more particularly, toa golf ball which includes a cover made from fast curing polyurethane.

[0003] Balata (trans-polyisoprene) was the primary material used forgolf ball covers until the late 1960's. Balata covered golf balls were(and are) preferred because of the soft feel and the control which thebetter player can impart to the ball. However, balata covered golf ballsare expensive, and difficult to produce. Balata balls also generallyexhibit poor cut resistance, which is also not beneficial.

[0004] In the late 1960's, ionomers were introduced by DuPont, under thetrade name Surlyn. Ionomers are copolymers of an olefin (generallyethylene), and an alpha-beta ethylenically unsaturated carboxylic acid(generally methacrylic acid). Neutralization of a number of the acidgroups is effected with metal ions, currently chosen from the group ofsodium, lithium, zinc and magnesium. Ionomer covers are more durablethan balata, and are currently the material of choice on most solidcore, and many wound core, golf balls. However, ionomer materials aregenerally harder than balata, and do not provide the golfer with thefeel and control of a balata covered golf ball.

[0005] In the mid-1980's, soft ionomers (known as Very Low ModulusIonomers or VLMI) were produced by DuPont. These ionomers are similar inchemical structure to standard ionomers, with the addition of anacrylate monomer to soften the material. These materials allowed for thedevelopment of softer ionomer covered golf balls, but did not produceproperties similar to balata.

[0006] Other soft thermoplastic materials (such as thermoplasticpolyurethanes, thermoplastic polyester elastomers, polyether block amidecopolymers, etc.) have been used as covers on golf balls, with limitedsuccess. Although these materials have been successfully used as mantle(inner cover) layers for golf balls, they generally produce insufficientresilience properties to be used as covers for premium golf balls. U.S.Pat. Nos. 5,688,191, 5,759,676, 5,810,678 and 5,813,923 all illustratethe use of a thermoplastic polyurethane material as a mantle material.Thermoplastic polyurethane materials have also been used in blends withother materials, such as ionomers. U.S. Pat. No. 4,674,751 describesblends of thermoplastic polyurethanes with ionomers.

[0007] More recently, wound golf balls made using castable polyurethanehave been developed. Balls made using castable polyurethane covers havemany properties comparable to balata—similar feel (slightly harder) andcomparable performance properties. Balls made using castablepolyurethane materials are available from Titleist (TitleistProfessional) and Maxfli (Maxfli Revolution).

[0008] U.S. Pat. No. 3,979,126 describes a polyurethane cover comprisinga prepolymer and curing agent having at least two amine groups. U.S.Pat. No. 3,989,568 describes a castable polyurethane material made withcuring agents having different rates of reaction to allow forpolyurethane to cure sufficiently to form half-shells, but not curecompletely. U.S. Pat. No. 4,123,061 also describes a polyurethanecompound that is cured sufficiently to form preform half-shells, but notcured to completion until molding of half shells around a wound core.U.S. Pat. No. 5,334,673 describes a castable polyurethane golf ballformed using a slow reacting polyamine curing agent. However, thepolyurethane covered golf balls described in this patent are made usinga casting process which is both difficult and time-consuming. U.S. Pat.Nos. 5,006,297, 5,733,428, 5,888,437 and 5,947,843 all describe variousmethods for molding slow curing polyurethane covered golf balls.

SUMMARY OF THE INVENTION

[0009] The invention provides a golf ball with a cover made using afast-curing thermoset polyurethane material produced from the reactionof two components: 1. an isocyanate, and 2. a mixture of isocyanatereactive compounds. The resulting golf ball yields comparableperformance properties (feel, resilience, spin rate) to golf balls madeusing balata or castable polyurethane covers. The golf ball can beproduced in a closed injection mold (Reaction Injection Molding)process, which is significantly less time-consuming, and more economicalthan standard castable polyurethane process of the prior art.

DESCRIPTION OF THE DRAWING

[0010]FIG. 1 is a sectional view of a three-piece wound golf ball with acover which is formed in accordance with the invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

[0011] Referring to FIG. 1, a three-piece golf ball 10 includes a center11, a layer of elastic windings 12, and a cover 13. The center can besolid or liquid filled and has a diameter within the range of 1 to 1.4inches, more preferably 1.0 to 1.25 inches. The windings can be formed,for example, from isoprene or natural rubber thread. The outer diameterof the layer of windings is within the range of 1.52 to 1.60 inches,more preferably 1.56 to 1.58 inches. According to the rules of theUnited States Golf Association, the outer diameter of the cover must beat least 1.680 inches.

[0012] The cover 13 is formed from a fast curing two-componentpolyurethane system comprising:

[0013] 1. an isocyanate;

[0014] 2. a mixture of isocyanate reactive compounds comprising one ormore of:

[0015] a. a polyether or polyester polyol;

[0016] b. aliphatic or aromatic amines or diamines;

[0017] c. chain extenders or crossliners;

[0018] d. catalysts;

[0019] e. internal mold release agents;

[0020] f. colorants fillers, and other standard cover ingredients.

[0021] The polyurethane cover has a Shore D hardness of 50 to 65.

[0022] Isocyanates suitable for use in this compound include (but arenot limited to) diphenylmethane-4,4′-diisocyanate (MDI) or an aliphaticisocyanate such as isophorone diisocyanate.

[0023] Polyether polyols suitable for use in the isocyanate reactivecompound include (but are not limited to) propylene glycol, glycerineand trimethylolpropane.

[0024] Polyester polyols suitable for use in the isocyanate reactivecompound include (but are not limited to) ethylene glycol, diethyleneglycol, and butanediol.

[0025] Chain extenders, catalysts, internal mold releases, colorants,etc. are used as needed.

[0026] A preferred construction for the golf ball is:

[0027] 1. a solid or liquid-filled center having diameter of 1.0-1.25inches;

[0028] 2. a center wound with isoprene or natural rubber thread to anoutside diameter of about 1.56 to 1.58 inches;

[0029] 3. a cover formed from a fast-curing polyurethane comprising twocomponents;

[0030] a. an aromatic isocyanate prepolymer (DiphenylmethaneDiisocyanate prepolymer) and

[0031] b. an isocyanate reactive compound, consisting of a polyol(propylene glycol), an aliphatic amine, an aromatic diamine(diethyltoluene diamine), and a catalyst (an organotin compound).

[0032] Polyurethane materials suitable for use as the cover arecommercially available from Bayer Corporation, under the trade nameBayer.

[0033] Table 1 lists the properties of polyurethane materials fromBayflex Corporation which are suitable for use in the invention. TABLE 1Specific Shore Flex. Mix Ratio Material Grade Gravity D Modulus Comp. AComp. B Bayflex 110-25 1.04 50 25,000 psi 47.5 100 Bayflex 110-35 1.0055 35,000 psi 52.9 100 Bayflex 110-50 1.04 58 52,000 psi 58 100

[0034] Golf balls were prepared in accordance with Table 2. The physicalproperties of the golf balls are also listed in Table 2. TABLE 2 Com-Shore C.O.R. Ball Center pression D 125 f/s 150 f/s 175 f/s I.V. Example1 Liquid 88 52 0.766 0.745 253.4 Examp1e 2 Solid 92 60 0.769 0.745 253.8Titleist Liquid 96.7 57 0.786 0.772 254.8 Professional Example 3 Solid104.9 54 0.793 0.774 0.749 255.7 Maxfli Solid 88.9 57 0.790 0.768 0.743256.5 Revolution

[0035] The ball of Example 1 was made using a liquid filled center(produced by Abbott Laboratories, and wound with Fulflex thread to adiameter of 1.57 inches. The cover was reaction injection molded fromBayflex 110-25 polyurethane.

[0036] The ball of Example 2 was made using a solid center, and wound toa diameter of about 1.57 inches. The cover was reaction injection moldedfrom Bayflex 110-50.

[0037] The ball of Example 3 was made using a solid center, and wound toa diameter of about 1.58 inches. The cover was reaction injection moldedfrom Bayflex 110-35.

[0038] The covers of all of the golf balls of the Examples wereinjection molded over the core using a Hennecke 55 Reaction InjectionMolding press and a single cavity mold. The Bayflex cover material wasmixed at a ratio consistent with the ratios described in Table 1, withthe following injection conditions:

[0039] 1. Throughput of about 35 g/s.

[0040] 2. Injection time set at 0.8 seconds.

[0041] 3. Mold temperature of 150° F.

[0042] 4. Isocyanate prepolymer pressure of about 2500 psi.

[0043] 5. Polyether Polyol system pressure of about 2000 psi.

[0044] The Bayflex grades used for these covers cure to sufficienthardness to allow demolding in about 10 seconds. The balls were actuallyremoved form the mold (in fully cured state) after about 30 seconds.

[0045] The ball of Example 1 was molded using Bayflex 110-25 fast curingpolyurethane system, tested for physical properties, and compared toTitleist Professional (a competitive golf ball made using a slow curing,castable polyurethane cover). Results indicate that the balls of Example1 yield comparable ball compression, slightly softer cover, and slightlylower resilience properties.

[0046] The ball of Example 2 was molded using Bayflex 110-50 fast curingpolyurethane system, tested for physical properties, and also comparedto the Titleist Professional ball. The Bayflex 110-50 cover resulted ina slightly higher Shore D hardness than the Titleist Professional, andcomparable compression and slightly lower resilience properties. Theresilience properties of Example balls 1 and 2, although slightly lowerthan the Titleist Professional, are still sufficient for a premium levelgolf ball.

[0047] The ball of Example 3 was molded using Bayflex 110-35 fast curingpolyurethane system, tested for physical properties, and compared toMaxfli Revolution (also a competitive golf ball made using a slowcuring, castable polyurethane cover). The ball of Example 3 yieldedslightly lower cover hardness (Shore D) and higher ball PGA compressionthan the Maxfli Revolution. The ball of Example 3 also yieldedcomparable resilience properties (Coefficient of Restitution, InitialVelocity) to the Maxfli Revolution.

[0048] Overall, the balls of Examples, 1, 2 and 3 illustrate that a ballwith the properties (cover hardness, PGA compression and resilienceproperties) required for a premium golf ball can be made using a fastcuring polyurethane cover material. The making of a polyurethane coverball using the cover described herein also allows for a much faster,easier, and less expensive method of processing than is necessary ifusing a slow curing, castable polyurethane cover.

[0049] Curing agents which are suitable for the fast curing polyurethanesystem are unhindered aromatic or aliphatic (di)amines. Morespecifically, the system includes an aromatic isocyanate and unhinderedaromatic (di)amines. Diethyltoluene diamine should be considered anunhindered diamine.

[0050] The polyurethane cover is preferably reaction injected moldedaround the wound center by placing the wound center in a two-part mold,closing the mold, mixing the two components of the polyurethane, andinjecting the mixed components into the closed mold. The details of thereaction injection molding apparatus and method are described inco-pending United States patent application entitled “Reaction InjectionMolded Golf Ball”, Serial No. 09/176,445, filed Oct. 21, 1998, which isincorporated herein by reference.

[0051] While in the foregoing specification a detailed description of aspecific embodiment of the invention was set forth for the purpose ofillustration, it will be understood that many of the details hereingivenmay be varied considerably by those skilled in the art without departingfrom the spirit and scope of the invention.

We claim:
 1. A golf ball comprising: a center, a layer of elasticwindings surrounding the center, a cover having a Shore D hardness of 50to 65 and formed from a fast curing two component polyurethane systemwhich includes:
 1. An isocyanate, and
 2. One or more isocyanate reactivecomponents selected from the class consisting of: a. polyether polyols,b. polyester polyols, c. aliphatic (di)amines, and d. aromatic(di)amines.
 2. The golf ball of claim 1 in which said polyurethanesystem is a thermoset polyurethane.
 3. The golf ball of claim 1 in whichsaid isocyanate is diphenylmethane 4,4-diisocyanate.
 4. The golf ball ofclaim 1 in which said isocyanate is isophorone diisocyanate.
 5. The golfball of claim 1 in which said polyurethane system includes an aromaticisocyanate, a polyol, an aliphatic amine, an aromatic diamine, and acatalyst.
 6. A golf ball comprising: a center having a diameter of 1 to1.4 inch, a layer of elastic windings surrounding the center and havingan outer diameter of 1.52 to 1.60 inch, and a cover having a Shore Dhardness of 50 to 65 and formed from a fast curing two componentpolyurethane system comprising:
 1. An aromatic isocyanate prepolymer, 2.an isocyanate reactive compound comprising a polyol, an aliphatic amine,an aromatic diamine, and a catalyst.
 7. The golf ball of claim 6 inwhich said aromatic isocyanate prepolymer is diphenylmethanediisocyanate prepolymer.
 8. The golf ball of claim 7 in which saidpolyol is propylene glycol.
 9. The golf ball of claim 8 in which saidaromatic diamine is diethyltoluene diamine.
 10. The golf ball of claim 6in which said polyol is propylene glycol.
 11. The golf ball of claim 6in which said aromatic diamine is diethyltoluene diamine.